My 1995 Sony ST-S361 was stuck in mute unless forced to mono. After the thread on thread on the Hitachi https://www.diyaudio.com/community/threads/hitachi-tuner-ft5500-mkii-display-out-by-0-05mhz.427933/ I though it might be similar.
This is what I found.
I could not tune the detactor coil to get close to zero across the test points.
I tested the the PLL accuracy with a spectrum analyser -the 7.2 MHz crystal and the LO were spot on - the tuner could really have benefited form a double sided PCB with a ground plane. It sprays RF from the PCB.
I thought the coil was faulty, but found that the service manual schematic was wrong - the coil connections were actually matchng the PCB markup, I added a 7pF ceramic in parallel with the built in capacitor and was able to get the coil tuned again. The built in MELF ceramic must have drifted off a little
This is what I found.
I could not tune the detactor coil to get close to zero across the test points.
I tested the the PLL accuracy with a spectrum analyser -the 7.2 MHz crystal and the LO were spot on - the tuner could really have benefited form a double sided PCB with a ground plane. It sprays RF from the PCB.
I thought the coil was faulty, but found that the service manual schematic was wrong - the coil connections were actually matchng the PCB markup, I added a 7pF ceramic in parallel with the built in capacitor and was able to get the coil tuned again. The built in MELF ceramic must have drifted off a little